Metal composition



Patented Mar. 9, 1943 METAL comosmon E ration of Delaware No Drawing.Application June 22 1940,

Serial No. 341,960

4 Claims.

This invention relates to a metallic composition and the manufacturethereof.

It is an object'of the invention to provide a material which will haveuseful properties for many applications and which will be particularlysuitable for electrical contacting members.

It is a further object of the present invention to provide an improvedcontacting material which will withstand severe loads withoutdisintegration.

It is a further object of the invention to provide a new metalcomposition and combination of metallic elements, resulting in a productof great cohesion.

Other objects of the invention will be apparent from the followingdescription, taken in connection with the appended claims.

The present invention comprises the combination of elements, methods ofmanufacture and the product thereof, brought out and exemplified in thedisclosure hereinafter set forth, the scope of the invention beingindicated in the appended claims. 1

While a preferred embodiment of the invention is described herein, it iscontemplated that considerable variation may be made in the methd ofprocedure and the combination of elements, without departing from thespirit of the invention.

' The invention contemplates the provision of a metallic body consistingof a carbide of a refractory metal taken from the fourth, fifth or sixthgroup of the periodic system, and cobalt and silver.

The complete composition may contain the combined ingredients in thefollowing permissible ranges of proportions:

The preferred carbides are tungsten carbide and molybdenum carbide. Theselection of the preferred composition to be used for any purpose will,of course, depend upon the specific properties desired such as degree ofhardness, electrical conductivity and conunder these conditions the mostdesirable range of compositions is as follows:

. Per cent Refractory metal carbide 35 to 49 Cobalt .25 to 15 Silver 50to 64 l5 1 Per cent Refractory metal carbide 50 to 70 Cobalt .25 toSilver to 49 20 The following are specific examples of preferredcompositions:

Per cent A. Refractory metal carbide Cobalt 2 05 Silver 58 B. Refractorymetal carbide 65- Cobalt 1 Silver at C. Refractory metal carbide Cobalt6 Silver; 44 D. Refractory metal carbide Cobalt 12 .Silver 28 5 In allof the above cases tungsten carbide and tact resistance, toughness andthe like for the particular application contemplated.

If high electrical conductivity is desired it is preferred that thesilver shall predominate and molybdenum carbide are the most importantand are generally preferred. However, the other carbides previouslymentioned all result in satis- Per cent carbides of metal selected fromthe factory. compositions, titan um carbide and zirgroup consisting oftitanium, zirco- 40 comum carblde bemg very useful mum, vanadium,columbium tanta In some cases silver base alloys containing mmmolybdenum and tungstn 35 to added ingredients which are not subversiveto Cobalt a 25 to 15 the desirable characteristics of the silver in thesilver to 64 compositions described may be used in place of silver andit is contemplated that the term silver shall be construed broadlyenough to cover both pure silver and sterling silver. Sterling silver issliver containing a relatively small proportion of copper which does notmaterially lower the electrical conductivity or adversely affect otherproperties such as low contact resistance, low material transfer and thelike when used for electric contact purposes.

A large number of tests have been made upon various compositionsprepared according to the present invention and it has been found thatthe compositions of refractory metal carbides, silver and cobaltcomingwlthin the scope of the present invention gave consistently betterperformance as contacts than compositions containing' no cobalt.

The compositions ofthe present inventionmay be prepared by mixing therefractory metal carbide powders with cobalt powder, then adding abinder such as 1% by weight of resin to facilitate pressing of the mixedpowders. The materials are then pressed into suitable shapes atrelatively high pressure, the pressure depending upon the degree ofporosity or density required. The pressed slugs are then sintered atsuitable temperatures such as 1100-1400 C. and for suitable periods suchas to 30 minutes in inert or reducing atmospheres. The sintered slugsare subsequently alloyed or impregnated with silver by placing asufficient quantity of silver upon the sintered pieces and heating to atemperature above the melting point of silver to cause fusion of thesilver and absorption of the molten silver into the voids in thesintered place due to capillary action.

It is also possible to mix the silver powders directly with the powderedrefractory metal carbides and cobalt powders and press the thoroughlymixed powders either cold or at. elevated temperatures into suitableshapes with or without a subsequent sintering operation at a suitabletemperature, preferably close to the melting point of silver, namely 960degrees C. Such compacts may also be further strengthened by applying acoining operation or cold forming operation after sintering.

It is also possible to add additional steps to the manufacturing processsuch as additional sintering and pressing operations at suitable stagesin the procedure so as to improve the strength or density of thematerial.

The composition produced in the manner described are susceptible to hotor cold forming operations. The hot working operations may compriseswaging,roiling, forging or drawing. It is advisable to use a smallreduction in area followed by annealing after which the reductions inarea may become progressively greater.

As an example of the manufacture of specific pressed until it had apressed density of approximately 8 to 8.2 grams per c. c. and was thensintered at 1200 degrees C. The density after sintering was found tohave increased to approximately 8.6 grams per c. c. The pieces were thenimpregnated with silver at a temperature of 1300 degrees C. Theresulting density was found to be approximately 13.4 grams per c. c.with a hardness of 34 to 39 Rockwell C. The electrical conductivity was34% and the silver content in the finished samples about 30%. Othercompositions were made up in which 1% cobalt was mixed with 99% tungstencarbide powder and in another of which 2% cobalt was mixed with a 98% oftungsten carbide, the rest otthe procedure being substantially the sameas describe and the results bein q ite similar.

While the present invention, as to its objects and advantages, has beendescribed herein as carried out in specific embodiments thereof, it isnot desired to be limited thereby. but it is intended to cover theinvention broadly within the spirit ann scope of the appended claims.

what'is claimed is:

1. An electric contacting element formed of a metal composition composedof 35 to 70% of refractory metal carbide selected from the groupconsisting of the carbides of titanium, zirconium, vanadium, columbium,tantalum, molybdenum and tungsten, .25 to 15% cobalt and 25 to 64%silver. 2. A metal composition comprising about of refractory metalcarbide selected from the group consisting of the carbides of titanium,zicronium, vanadium, columbium, tantalum, molybdenum and tungsten, about12% cobalt and about 28% silver.

3. A metal composition comprising about 40% of refractory metal carbidesselected from the group consisting of the carbides of titanium,zirconium, vanadium, columbium, tantalum,

molybdenum and tungsten, about 2% cobalt an about 58% silver.

4. A metal composition comprising about of refractory metal carbidesselected from the group consisting of the carbides of titanium,zirconium, vanadium, columbium, tantalum, molybdenum and tungsten, about1% cobalt and about 34% of silver.

FRANZ R. HENSEL.

EARL I. LARSEN.

EARL F. SWAZY.

